While we were in France my mobile phone uses french networks, and we seem to randomly change between them, sometimes while staying in the same place!
It doesnt seem to make much difference, I dont use the phone much on holiday, and then mostly for texting.
When we got back to Portsmouth and were heading back up the motorway I was hugely entertained to recieve the following message from O2, my network.
"Thankyou for travelling with o2 in Iceland"
Iceland!!!!! I was in France